[ Previous | Next | ADS ]

Swift follow-up observation of the detection of a gamma-ray enhanced emission from the FSRQ PKS 1510-089

ATel #3910; S. Vercellone, P. Romano (INAF/IASF-Pa), F. Verrecchia, C. Pittori (ASDC), M. Cardillo (INAF/IASF-Rm and Univ. Roma Tor Vergata), E. Striani (Univ. Roma Tor Vergata), I. Donnarumma (INAF/IASF-Rm), A. Bulgarelli (INAF/IASF-Bo) and M. Tavani (INAF/IASF-Rm and Univ. Tor Vergata) on behalf of the AGILE Team
on 3 Feb 2012; 17:18 UT
Credential Certification: Stefano Vercellone (stefano@ifc.inaf.it)

Subjects: Optical, Ultra-Violet, X-ray, Gamma Ray, AGN, Blazar

Referred to by ATel #: 3934, 3939

Following the AGILE/GRID detection of a gamma-ray enhanced emission from the FSRQ PKS 1510-089 (Verrecchia et al. 2012, ATel #3907), we performed a Swift target of opportunity observation. Swift observed PKS 1510-089 from 2012-02-02 19:49:09 to 2012-02-02 20:30:29 UT for about 2.5 ks.

The XRT spectrum (PC data, 2.4 ks integration) fitted with an absorbed power law with an absorbing column density fixed to the Galactic value of 6.89E20 cm-2 (Kalberla et al. 2005) yields a photon index of 1.3+/-0.2, and an average flux of F=9.7E-12 erg/cm2/s (2-10 keV, unabsorbed).

The UVOT observed the field simultaneously with the XRT in all optical and UV filters. The preliminary observed magnitudes in the Vega system are:
V 16.69+/-0.06 (stat) +/-0.01 (sys)
B 16.80+/-0.04 (stat) +/-0.02 (sys)
U 15.79+/-0.04 (stat) +/-0.02 (sys)
UVW1 15.98+/-0.04 (stat) +/-0.03 (sys)
UVM2 15.88+/-0.03 (stat) +/-0.03 (sys)
UVW2 15.91+/-0.03 (stat) +/-0.03 (sys)
The magnitudes in the table are not corrected for the Galactic extinction due to a reddening of E(B-V) = 0.097 mag in the direction of the source (Schlegel et al. 1998).

We can compare our preliminary results with those discussed in D'Ammando et al., (2011, A&A, 529, A145) obtained during a very high and prolonged gamma-ray state in 2009 March, when PKS 1510-089 reached a gamma-ray peak flux of F=(702+/-131)E-8 ph/cm2/s (E>100 MeV), about a factor of 2.8 higher than that reported in ATel #3907. We note that our current X-ray flux F=1.3E-11 (0.3-10 keV, unabsorbed) and photon index, 1.3+/-0.2, are consistent with the harder-when-brighter trend reported in Figure 2 of D'Ammando et al. (2011).

We warmly thank N. Gehrels, the Science Planners, and the Observatory Duty Scientists for having scheduled this observation in such a timely way.